Agricultural irrigation systems are widely used as part of the continuing effort to produce more food on the available agricultural land. A major requirement of a successful irrigation system is that it must be possible to determine reasonably accurately how much water has been applied to the land. If too little is applied then there is the likelihood of a yield which is below that which could otherwise be expected. If too much is applied there is certainly a wastage of water and there is also a possibility that overwatering will also lower the yield.
With commercially available non-pressure compensating irrigation emitters (emitters come in the form of sprinklers or drippers), the rate of flow through an emitter at a particular pressure can obviously be determined by calculation or experimentally. Unfortunately, in many irrigation systems, inlet pressure varies widely due mainly to differences in elevation but also with time. With simple non-pressure compensating emitters, the rate of flow varies very substantially with changes in pressure.
In order to overcome this problem, quite complex emitters have been proposed which are sensitive to pressure variations and which, by bringing orifices of different sizes into use, usually by diaphragms or springs, compensate for changes in pressure. Such emitters are delicate and consequently prone to damage by the environment and when handled by manual labourers in the field.
The object of the present invention is to provide a pressure compensating, water flow control device which is simple in construction and provides a rate of water flow which is substantially constant regardless of inlet pressure.